If PROVIDER_OFFSET is non-zero in shorewall.conf(5), then
the value must be a multiple of 2^^PROVIDER_OFFSET. In all cases,
the number of significant bits may not exceed PROVIDER_OFFSET +
PROVIDER_BITS.

DUPLICATE -
routing-table-name

The name of an existing table to duplicate to create this
routing table. May be main or the name of a
previously listed provider. You may select only certain entries from
the table to copy by using the COPY column below. This column should
contain a dash ("-') when USE_DEFAULT_RT=Yes in shorewall.conf(5).

INTERFACE -
interface[:address]

The name of the network interface to the provider. Must be
listed in shorewall-interfaces(5).
In general, that interface should not have the
proxyarp or proxyndp option
specified unless loose is given in the OPTIONS
column of this entry.

Important

For IPv6, if the interface is an Ethernet device and an IP
address is supplied, it should be the upstream router's link-level
address, not its global address.

Where more than one provider is serviced through a single
interface, the interface must be followed by a
colon and the IP address of the interface that
is supplied by the associated provider.

GATEWAY - {-|address[,mac]|detect|none}

The IP address of the provider's gateway router. Beginning
with Shorewall 4.6.2, you may also specify the MAC address of the
gateway when there are multiple providers serviced through the same
interface. When the MAC is not specified, Shorewall will detect the
MAC during firewall start or restart.

You can enter detect here and
Shorewall will attempt to detect the gateway automatically.

Beginning with Shorewall 5.0.6, you may also enter none. This causes creation of a routing table
with no default route in it.

For PPP devices, you may omit this column.

OPTIONS (Optional) - [-|option[,option]...]

A comma-separated list selected from the following. The order
of the options is not significant but the list may contain no
embedded white-space.

autosrc

Added in Shorewall 4.5.17. Causes a host route to the
provider's gateway router to be added to the provider's
routing table. This is the default behavior unless overridden
by a following noautosrc
option.

track

If specified, inbound connections on this interface are
to be tracked so that responses may be routed back out this
same interface.

You want to specify track if internet
hosts will be connecting to local servers through this
provider.

Beginning with Shorewall 4.4.3, track
defaults to the setting of the TRACK_PROVIDERS option in
shorewall.conf
(5). If you set TRACK_PROVIDERS=Yes and want to override that
setting for an individual provider, then specify
notrack (see below).

balance[=weight]

The providers that have balance
specified will get outbound traffic load-balanced among them.
By default, all interfaces with balance
specified will have the same weight (1). You can change the
weight of an interface by specifying
balance=weight
where weight is the weight of the
route out of this interface.

Prior to Shorewall 5.1.1, when USE_DEFAULT_RT=Yes,
balance=1 is assumed unless the
fallback, loose,
load or tproxy option is
specified. Beginning with Shorewall 5.1.1, when
BALANCE_PROVIDERS=Yes, balance=1 is assumed
unless the fallback, loose,
load or tproxy option is
specified.I

Caution

In IPV6, the balance option does not
cause balanced default routes to be created; it rather
causes a sequence of default routes with different metrics
to be created.

loose

Shorewall normally adds a routing rule for each IP
address on an interface which forces traffic whose source is
that IP address to be sent using the routing table for that
interface. Setting loose prevents creation of
such rules on this interface.

load=probability

Added in Shorewall 4.6.0. This option provides an
alternative method of load balancing based on probabilities.
Providers to be balanced are given a
probability (a number 0 > n
>= 1) with up to 8 digits to the right of the decimal
point. Beginning with Shorewall 4.6.10, a warning is issued if
the sum of the probabilities is not 1.00000000.

noautosrc

Added in Shorewall 4.5.17. Prevents the addition of a
host route to the provider's gateway router from being added
to the provider's routing table. This option must be used with
caution as it can cause start and restart failures.

notrack

Added in Shorewall 4.4.3. When specified, turns off
track.

optional (deprecated for use with
providers that do not share an interface)

If the interface named in the INTERFACE column is not up
and configured with an IPv4 address then ignore this provider.
If not specified, the value of the optional
option for the INTERFACE in shorewall-interfaces(5)
is assumed. Use of that option is preferred to this one,
unless an address is provider in
the INTERFACE column.

primary

Added in Shorewall 4.6.6, primary is equivalent to balance=1 and is preferred when the
remaining providers specify fallback or tproxy.

src=source-address

Specifies the source address to use when routing to this
provider and none is known (the local client has bound to the
0 address). May not be specified when an
address is given in the INTERFACE
column. If this option is not used, Shorewall substitutes the
primary IP address on the interface named in the INTERFACE
column.

mtu=number

Specifies the MTU when forwarding through this provider.
If not given, the MTU of the interface named in the INTERFACE
column is assumed.

fallback[=weight]

Indicates that a default route through the provider
should be added to the default routing table (table 253). If a
weight is given, a balanced route
is added with the weight of this provider equal to the
specified weight. If the option is
given without a weight, an separate
default route is added through the provider's gateway; the
route has a metric equal to the provider's NUMBER.

Prior to Shorewall 4.4.24, the option is ignored with a
warning message if USE_DEFAULT_RT=Yes in
shorewall.conf.

Caution

In IPV6, specifying the fallback
option on multiple providers does not cause balanced
fallback routes to be created; it rather causes a sequence
of fallback routes with different metrics to be
created.

tproxy

Added in Shorewall 4.5.4. Used for supporting the TPROXY
action in shorewall-mangle(5). See http://www.shorewall.net/Shorewall_Squid_Usage.html.
When specified, the MARK, DUPLICATE and GATEWAY columns should
be empty, INTERFACE should be set to 'lo' and
tproxy should be the only OPTION. Only one
tproxy provider is allowed.

hostroute

Added in Shorewall 4.5.21. This is the default behavior
that results in a host route to the defined GATEWAY being inserted into the main
routing table and into the provider's routing table. hostroute is required for older
distributions but nohostroute
(below) is appropriate for recent distributions. hostroute may interfere with Zebra's
ability to add routes on some distributions such as Debian
7.

nohostroute

Added in Shorewall 4.5.21. nohostroute inhibits addition
of a host route to the defined GATEWAY being inserted into the main
routing table and into the provider's routing table. nohostroute is not appropriate for
older distributions but is appropriate for recent
distributions. nohostroute
allows Zebra's to correctly add routes on some distributions
such as Debian 7.

persistent

Added in Shorewall 5.0.2 and alters the behavior of the
disable command:

The provider's routing table still contains the
apprioriate default route.

Unless the noautosrc option is
specified, routing rules are generated to route traffic
from the interfaces address(es) out of the provider's
routing table.

Note

The generated script will attempt to reenable a
disabled persistent provider during execution of the
start, restart and
reload commands. When
persistent is not specified, only the
enable and reenable
commands can reenable the provider.

Important

RESTORE_DEFAULT_OPTION=Yes in shorewall[6].conf is not
recommended when the persistent option is
used, as restoring default routes to the main routing table
can prevent link status monitors such as foolsm from
correctly detecting non-working providers.

COPY -
[{none|interface[,interface]...}]

A comma-separated list of other interfaces on your firewall.
Wildcards specified using an asterisk ("*") are permitted (e.g.,
tun* ). Usually used only when DUPLICATE is main.
Only copy routes through INTERFACE and through interfaces listed
here. If you only wish to copy routes through INTERFACE, enter
none in this column.

Beginning with Shorewall 4.5.17, blackhole, unreachable and
prohibit routes are no longer copied by default but may be copied by
including blackhole,unreachable and prohibit respectively in the COPY
list.

Examples

IPv4 Example 1:

You run squid in your DMZ on IP address 192.168.2.99. Your DMZ
interface is eth2